SLAAET6 August   2025

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1S-Parameter Definition
    1. 1.1 Insertion Loss (S21)
    2. 1.2 Return Loss (S11)
  5. 2High-Speed Signal Design Example Of FPD-Link™ Serializer Body
    1. 2.1 Design Example Overview
    2. 2.2 Key Points in High-Speed FPD-Link Layout Design
  6. 3Factors Impacting Return Loss and Optimization Guidelines
    1. 3.1 Transmission Line Impedance Impact
    2. 3.2 AC Coupling Capacitor Landing Pad Impact And Optimization
      1. 3.2.1 Mitigation Strategy: Anti-Pad Implementation
      2. 3.2.2 Simulation Results With Ansys® HFSS
    3. 3.3 Through-Hole Connector Footprint Impact and Optimization
      1. 3.3.1 Through-Hole Connector Via Anti-Pad Impact
        1. 3.3.1.1 Simulation Results With Ansys® HFSS
      2. 3.3.2 Surrounding Ground Vias Impact
        1. 3.3.2.1 Simulation Results (Surrounding Ground Vias Impact)
      3. 3.3.3 Non-Functional Pad Impact
        1. 3.3.3.1 Simulation Results (Non-Functional Pad Impact)
    4. 3.4 Generic Signal Via Impact and Optimization
      1. 3.4.1 Simulation Results
    5. 3.5 ESD Diode Parasitic Capacitance Impact and Optimization
  7. 4Summary

3.3.1.1 Simulation Results With Ansys® HFSS

This section shows the simulation results using Ansys HFSS:

  • Figure 3-5: Simulation model of the through-hole connector signal via
  • Figure 3-7: Return loss (S11) simulation result with different connector via anti-pad size
  • Figure 3-7: TDR impedance simulation result with different connector via anti-pad size

Both excessive anti-pad size and insufficient size can cause significant decrease or increase on the signal impedance and result in degraded return loss.

Anti-pads have a diameter of 42mil in this design example, reducing impedance variation and increasing return loss performance.

Simulation Model Of the Through-Hole Connector Signal Via Figure 3-5 Simulation Model Of the Through-Hole Connector Signal Via
Return Loss (S11) With Different Connectors Via Anti-Pad Size Figure 3-6 Return Loss (S11) With Different Connectors Via Anti-Pad Size
TDR Impedance With Different Connectors Via Anti-Pad Size Figure 3-7 TDR Impedance With Different Connectors Via Anti-Pad Size